In the field of arboriculture, there are many techniques that are implemented for training young trees such as fruit trees) to develop a proper number of wide-angled scaffold branches in a desirable arrangement along the trunk of the tree. In arboricultural terminology, a scaffold branch is one of the primary limbs radiating from the main trunk (or stem) of a tree. All subordinate branches (such as lateral branches) stem from the scaffold branches. With the proper training of young fruit trees, these trees can eventually develop, over time, a desirable amount and arrangement of scaffold branches, resulting in fruit trees that can produce high yields of quality fruit.
In general, scaffold, branches of fruit trees must be strong enough to support their own weight plus heavy crop loads (fruit) that grow on these branches, without splitting and breaking. The strength of a scaffold branch is based, in part, on the angle of attachment (referred to as “crotch angle”) between the scaffold branch and the main tree trunk. Typically, scaffold branches having a wide crotch angle of attachment with the main tree trunk are much stronger than scaffold branches having narrow crotch angle of attachment with the main trunk. By way of example, FIGS. 1A and 1B illustrate scaffold branches with different crotch angles. In particular, FIG. 1A illustrates a portion of a tree having a main trunk (1) and a scaffold branch (2) with a very narrow crotch angle A, while FIG. 1B illustrates a portion of a tree having a main trunk (1) and a scaffold branch (2) with a wider narrow crotch angle A.
Typically, scaffold branches grow about 30 to 45 degrees above the horizontal. However, scaffold branches having a relatively wide crotch angle of attachment are much stronger than those with a relatively narrow crotch angle of attachment because a wide crotch angle allows strong connective wood to form in the crotch as well as on the sides and the lower portion of the scaffold branch attachment. On the other hand, scaffold branches having tighter crotch angles of attachment with the main trunk have tendency to be weaker for various reasons.
For example, as a tree grows, a scaffold branch having a narrow crotch angle of attachment may result in bark becoming imbedded deep within the crotch between the scaffold branch and tree trunk. This growth is referred to as “included bark.” The growth of included bark weakens the attachment of the scaffold branch to the trunk because little or no connective wood forms in a sharp-angled crotch, which can lead to branch failure when the tree matures. While scaffold branches having smaller crotch angle attachments may be strongly attached in their early years, as these branches grow and become heavier and more spread out, the branches are more inclined to split at the crotch due to, e.g., increased weight or external forces caused by rain, snow storms or winds. For example, FIG. 2 illustrates a tree wherein a mature scaffold branch (2) having many lateral branches (3) splits from the main trunk (1) due to weakness caused by a narrow crotch angle.
Furthermore, scaffold branches having tighter crotch angles of attachment with the main trunk have tendency to be weaker due to pathogens. In particular, when a scaffold branch has a crotch angle of attachment that is 45 degrees or less, the crotch meeting with the stem/trunk, is a pathway for diseases, which result from insects or airborne viruses, to enter the cambium of the tree and eventually cause the branch or the rest of the tree to die. Thus, in training a young tree, it is important to train scaffold branches to develop wide angles of attachment.
Conventional methods for training scaffold branches to form wide crotch angles make use of spring-type wooden clothespins which serve as braces that are positioned between the trunk and young scaffold branches to force the branches to form wide crotch angles with the main axis of the tree. However, clothespins do not provide a sturdy brace structure and are easily pushed upwards as the scaffold branch grows, thus forming a much less desirable “tighter” crotch angle. Moreover, the use of clothespins are problematic in the use of training young scaffold branches as the clothespins serving as braces can be easily dislodge from, or otherwise knocked off the tree due to bad weather conditions or animals.